The xe2x80x9cPrecure Magnetic Switchxe2x80x9d is of the proximity type because it is actuated by an unconnected remote source. Either by ferreous metal or by magnetic material.
Said switch functions by gravitational pull and magnetic force.
The switch housing (N) and (L) are one piece. Injection molded from black ABS ultraviolet resistant plastic. The other housing part (not shown) is a half circle cover from the same material. The weather proof terminal cap (O) being the last part made from this material.
The non-conducting shaft (A) is made from ordinary injection molding plastic.
Magnet (B), 0.375xe2x80x3 O.D.xc3x972.000xe2x80x3 rod is made from cobalt.
Contacts (C), (D), and (E) are made from carbon with 1.625 braided copper leads (CL) and (EL) attached.
Axles (F) and (Fb) are from 0.125 brass rod machined to approximately a 60 point on one end approx. 0.375xe2x80x3 long.
Brass bearing and conductor (J) is a 0.250xe2x80x3xc3x971.375xe2x80x3 threaded brass rod, locked in place with a 0.250 brass lock nut. (J) is counter sunk on one end approx. 70 degrees to receive axle (F). (J) also serves as a xe2x80x9cTake-upxe2x80x9d to remove slack between bearings and axles.
Bearing (Ja) is a 0.125 dia. round head brass rivet with its head counter sunk approx. 70 degrees to receive axle (Fb).
(EA) and (CA) are #10 brass machine round head screws with lock nuts. These serve as terminals and connectors for contact leads (CL) and (EL).
The xe2x80x9cPrecure Magnetic Switchxe2x80x9d is shown in FIG. 1 with the switch housing (N) in normally open circuit mode with indicator point (G) in the vertical position. The longer portion of magnet (B) being heavier holds moveable contact (D) equidistant from fixed contacts (C) and (E).
In FIG. 2, as the switch is moved adjacent to permanent bar magnet (M), FIG. 5, the rod magnet (B) is drawn to field magnet (M) thereby rotating shaft (A) counter clockwise causing moveable contact (D) to come against fixed contact (C) thus completing the circuit.
Conversely by rotating magnet (M), FIG. 5 180 degrees to reverse polarity, magnet (B) is pushed from magnet (M) thereby rotating shaft (A) clockwise to complete the circuit between (D) and (E).
The switch is illustrated in FIG. 3 with the switch housing (N) having been rotated counter clockwise around it""s axis until indicator (H) is in the vertical position. The heavier portion of magnet (B) is holding moveable contact (D) against fixed contact (E) for the normally closed circuit operation.
In FIG. 4, as the switch is moved adjacent to field magnet (M), FIG. 6, magnet (B) is pulled, rotating shaft (A) counter clockwise to break circuit between moveable contact (D) and fixed contact (E).
FIG. 7 clarifies the location of magnet (B) relative to position of moveable contact (D). 7 also illustrates how axles (F) and (Fb) are installed into shaft (A) and into bearings (J) and (Ja).
Also in FIG. 7, we see how the electrical current is passed through bearing (J) (now serving as the common terminal), to axle (F), to moveable contact (D). Shaft (A) insulates parts (B), (Fb), and (Ja) from the electrical current.
FIG. 8 illustrates terminal cover (O), being a cylinder with one end open which fits over the terminal end housing (L) shown in FIG. 7.
Historically many methods of controlling electrical currents have been used. It has been found that Using magnets to open and close circuits is among the simplest of the systems. Shlesinger, (U.S. Pat. No. 3,760,312) uses a powered rotating permanent magnet. This is one solution to timed circuit actuation. Paulet, (U.S. Pat. No. 4,199,741) provided a solution to the high driving torque of rotary switches. Lerner et. al. (U.S. Pat. No. 4,353,049) gives us a magnetic detent system instead of the old spring and ball. Johnson, (U.S. Pat. No. 4,481,389) furnishes an excellent magnetic control device utilising a closely adjacent actuating permanent magnet.
In some fields, such as in the motion and position control of xe2x80x9cCenter Pivotxe2x80x9d irrigation machines there is a need for a sensitive non mechanical, non manual, non powered method of circuit control. A system whereby xe2x80x9cswitchingxe2x80x9d can be controlled by utilising a permanent magnet from a greater distance than before. The invention has made a substantial advancement in this area.
Center pivot irrigation is a well-known and widely used method of applying water on cropland.
There are several methods of controlling the operation of these systems. Controlling is the method of halting or reversing the rotation of the outer end of the pivot system at a given point in the cropland.
No automatic control. The system moves in either clockwise or counter clockwise mode.
The operator must be at xe2x80x9cthe right place at the right time.xe2x80x9d Day or night. To shut down or reverse the system.
A micro switch mounted at the pivot leg. Activated by adjustable trigger located on the pivot ring.
This allows the operator to stop or reverse the system by moving the trigger to the imaginary compass point on the ring relative to the stopping or reverse point of the outer end of the machine.
However with this method the outer end of the system never stops or reverses at the same point.
Due to frictional differences in changing soil conditions, the drive wheels on the end tower will loose or gain traction. This will cause the end tower to loose or gain distance relative to the given stop or reverse point of the outer end. This can affect accuracy by 20 to 50 feet.
Computer controlled at the pivot. This system was developed around 1988. But has fallen out of favor due to being a serviceman""s nightmare. And to being initially expensive to install. Also the control module is very expensive and subject to burn out by lightning.
The moveable barrier method involves mounting four micro-switches at the center of the end tower.
These switches are actuated mechanically by two three-foot long hanging trigger arms. These in turn move a rod fore and or aft. Said rod is attached to a cam, which operates the micro switches.
This method of control necessitates the placing of portable trigger points in the field. They are called barriers. The barriers are usually made from 1xc2xdxe2x80x3 xe2x80x9cor 2xe2x80x3xe2x80x9d steel pipe. They are constructed in an xe2x80x9cLxe2x80x9d shape and weigh as much as one hundred fifty pounds.
The longer and heavier of the L""s leg is placed horizontally on the ground directly in the path and with it""s end against the movement of the end tower""s drive wheels.
As the end tower arrives at the barrier. The drive wheel rolls upon the horizontal leg. Thereby holding the barrier steady as the trigger arm pushes against the vertical leg of the barrier.
This method is complicated and expensive to build and install. Moving the barriers is difficult and cumbersome. Especially after the weight of the end tower has buried the horizontal leg into the mud.
And if the crop is of a tall nature as is corn. The hanging trigger arms can foul in the stalks, causing the system to prematurely stop or reverse.
IF the switches fail to function the end tower usually rolls up on the barrier. This can cause the end tower to up end. Resulting in great expense in repairs and down time.
An electrical switch having a contact and permanent magnet affixed to a rotating shaft mounted on an axis between two stationary contacts. Whose radii corresponds with that of the shaft mounted contact. Whose rotation responds to the polarity of a remote adjacent permanent bar magnet, causing the rotating shaft mounted contact to meet, or leave one or the other stationary contacts to complete or break the circuit. All the above described parts (excepting the remote permanent bar magnet) encased within a non conductive plastic housing.